Finding the Fourth Proportional to 109.86, 151.38 and 78.72

Step by Step Solution

1. Step 1: Write the proportion equation
   109.86 : 151.38 = 78.72 : x
2. Step 2: Convert to fraction form
   109.86/151.38 = 78.72/x
3. Step 3: Cross multiply
   109.86x = 151.38 × 78.72
4. Step 4: Simplify right side
   109.86x = 11,916.63
5. Step 5: Solve for x
   x = 11,916.63/109.86
6. Step 6: Final answer
   x = 108.47